The invention relates to the field of vehicle drive systems. It relates more specifically to the detection of faults in the circuit of the gasoline vapor filter (also known as “canister”) that is fitted to vehicles equipped with an internal combustion gasoline engine.
For many years, with a view, amongst other things, to reduce the pollution generated by gasoline engine vehicles, and at the same time to reduce their fuel consumption, the fuel tanks of these vehicles have been fitted with a device that recovers the gasoline vapors and reinjects them into the engine. This device, usually known to those skilled in the art as a canister, is situated near to the gasoline tank. It comprises a charcoal filter which fixes the gasoline vapors, notably when the engine is at a standstill. The injection of the vapors into the engine via the inlet pipe is commanded by the engine control unit (ECU) which enables the opening and closing of a purge valve.
Current standards in certain countries require the ability to detect the presence of leaked gasoline vapors in a vehicle. This entails diagnosing all possible leaks and faults of the components involved, notably the gasoline vapor filter (canister) and the purge valve.
Methods for detecting the operation of the purge valve using a test performed when the vehicle is at idle are known from the prior art. In these methods, a series of openings and closings of the purge valve are commanded, over a period of around ten seconds. If the valve is operational, then the admission of gasoline vapor to the engine should result in a change in various operating parameters such as the richness of the mixture, the torque, the engine speed, the inlet pressure, etc. The methods then detect whether one of these parameters, which may depend on the vehicle concerned, varies beyond a predetermined threshold, and this variation then validates correct operation of the vapor filter purge valve. Such a method is, for example, described in patent application FR 2 900 981 in the name of Siemens VDO Automotive.